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An extreme case of galaxy and cluster co-evolution at z  = 0.7

Ebeling, H; Richard, J; Smail, I; Edge, AC; Koekemoer, AM; Zalesky, L

An extreme case of galaxy and cluster co-evolution at z  = 0.7 Thumbnail


H Ebeling

J Richard

AM Koekemoer

L Zalesky


We report the discovery of eMACS J0252.4−2100 (eMACS J0252), a massive and highly evolved galaxy cluster at z = 0.703. Our analysis of Hubble Space Telescope imaging and VLT/MUSE and Keck/DEIMOS spectroscopy of the system finds a high-velocity dispersion of 1020+180−190 km s−1 and a high (if tentative) X-ray luminosity of (1.2 ± 0.4) × 1045 erg s−1 (0.1–2.4 keV). As extreme is the system’s brightest cluster galaxy, a giant cD galaxy that forms stars at a rate of between 85 and 300 M⊙ yr−1 and features an extended halo of diffuse [O II] emission, as well as evidence of dust. Its most remarkable properties, however, are an exceptionally high ellipticity and a radially symmetric flow of gas in the surrounding intracluster medium, potential direct kinematic evidence of a cooling flow. A strong-lensing analysis, anchored by two multiple-image systems with spectroscopic redshifts, finds the best lens model to consist of a single cluster-scale halo with a total mass of (1.9 ± 0.1) × 1014 M⊙ within 250 kpc of the cluster core and, again, an extraordinarily high ellipticity of e = 0.8. Although further, in-depth studies across the electromagnetic spectrum (especially in the X-ray regime) are needed to conclusively determine the dynamical state of the system, the properties established so far suggest that eMACS J0252 must have already been highly evolved well before z ∼ 1, making it a prime target to constrain the physical mechanisms and history of the co-evolution or dark-matter haloes and baryons in the era of cluster formation.


Ebeling, H., Richard, J., Smail, I., Edge, A., Koekemoer, A., & Zalesky, L. (2021). An extreme case of galaxy and cluster co-evolution at z  = 0.7. Monthly Notices of the Royal Astronomical Society, 508(3), 3663-3671.

Journal Article Type Article
Acceptance Date Sep 16, 2021
Online Publication Date Sep 23, 2021
Publication Date 2021-12
Deposit Date Oct 27, 2021
Publicly Available Date Dec 8, 2021
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 508
Issue 3
Pages 3663-3671
Related Public URLs


Published Journal Article (4.3 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021, The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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